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Boiler Plant Operations
Published in Carl Bozzuto, Boiler Operator's Handbook, 2021
After the boiler is filled with water, it is time to start a burner cycle, which always begins with establishing and proving air flow through the burner and furnace. In very small boilers, like a home hot water heater, air flow is a function of combustion and is not proven. In most boilers, however, it amounts to starting a fan which will produce a measurable air flow that can be proven. The proof typically consists of a fan motor starter interlock contact and an air flow switch. The key words are air flow switch. On many systems, a simple pressure switch is used. Pressure does not prove that there is flow. Sometimes, a simple wind box pressure switch is used to proveacombustion air flow. Its contacts will close when the fan runs and will open when the fan is shut down because a pressure switch simply compares pressure at the point of connection and atmospheric pressure. If one of those switches is giving problems, it can usually be made to function by closing the burner register. This should not be done. There is no air flow through the burner when the register is shut, but the switch has been made. Air flow should be proven by a means that is independent of such conditions. One of the best methods is using the differential pressure across a fixed (not adjustable) resistance somewhere in the air flow stream.
Electrolyzer systems
Published in Leonard W. Casson, James W. Bess, Conversion to On-Site Sodium Hypochlorite Generation, 2019
Leonard W. Casson, James W. Bess
Air-cooled DC rectifiers are sometimes supplied with a fan pressure switch as a substitute for a vane type air flow switch or a pitot tube. Pressure switches can only be installed in equipment having an internal baffle at the diodes or thyristors to assure sufficient pressure. This pressure is a differential pressure measurement referenced to atmospheric pressure. Experience has demonstrated the necessity for a spare differential pressure switch available on-site. These switches are measuring pressure differences of 1/4- to 3 / 4 -inch water column against atmospheric conditions, are in generally harsh environments, and are prone to develop sticky diaphragm failures over extended operating times. Cooling fan motors and oil or water circulation pump motors are always supplied with their own safety circuits in accordance with local code requirements.
Boiler Plant Operations
Published in Kenneth E. Heselton, Boiler Operator’s Handbook, 2020
After the boiler is filled with water it’s time to start a burner cycle which always begins with establishing and proving air flow through the burner and furnace. In very small boilers, like your home hot water heater, airflow is a function of combustion and is not proven. In most boilers, however, it amounts to starting a fan which will produce a measurable air flow that can be proven. Proof typically consists of a fan motor starter interlock contact and an air flow switch.
Dual space vector PWM technique for a three-phase to five-phase quasi Z-source direct matrix converter
Published in Automatika, 2022
S. Manivannan, N. Saravanakumar, K. N. Vijeyakumar
Figure 1 shows the main circuit configuration of QZSDMC. It’s consisting of a three-phase source, input filter, QZS network, direct matrix converter and five-phase RL load. The QZS network consisting of six inductors named Lax, Lbx, Lcx (where x = 1, 2), six capacitors named as Cax, Cbx, Ccx (where x = 1, 2) and three bidirectional switches Sy (where y = a,b,c) with the same switching states, as a result, the switching signal is represented as S0. All inductors having equal values as well as all the capacitors are having equal values [36]. The three-phase to five-phase power circuit topology is connected in series with the Z-source network as presented in Figure 1. For five-phase, it consists of five legs and each consisting of bidirectional switches. The bidirectional power flow switches consist of two power diodes and two IGBT switches. The power diode and IGBTs are connected in series and the entire switching configuration should be connected in a common-emitter configured bidirectional power flow switch as available in Figure 2 [37]. The output configuration should be odd in phases. The nature of the load connected to the power circuit should be RL load.
Three-phase power conversion using quasi Z source direct matrix converter (QZSDMC) for fixed frequency to variable frequency using direct duty ratio based pulse width modulation technique
Published in International Journal of Electronics, 2022
S Manivannan, N Saravanakumar, K N Vijeyakumar
The Figure 2 shows the main circuit arrangement of QZSDMC. It is consisting of a three-phase source, input filter, QZS-network, direct matrix converter and three-phase RL-load. The QZS network consists of six inductors, namely, Lax, Lbx and Lcx (where x = 1, 2), six capacitors, namely, Cax, Cbx and Ccx (where x = 1, 2) and three bi-directional switches Sy (where y = a,b,c) with the same switching states; as a result, the switching signal is represented as S0. All inductors are having equal values as well as all the capacitors are having equal values. The three-phase to three-phase power circuit topology is connected in series with the Z-source network system as shown in Figure 2. For three-phase, it consists of three legs and each leg has a series of connections of three bi-directional switches. The bidirectional power flow switches consist of two power diodes and two IGBT switches. The power diode and IGBTs are connected in series and the entire switching configuration should be connected in a common emitter configured bidirectional power flow switch as shown in Figure 3. The output configuration should be odd in phases. The nature of the load connected to the power circuit should be RL load.
A Survey on Packet Switching Networks
Published in IETE Journal of Research, 2022
SDN includes a variety of technologies, such as automation across programmability, network virtualization, and functional separation. Initially, the SDN was solely based on the decoupling of the DP from the CP. The DP is responsible for flowing packets from one hop to another hop while the CP decides the movement of the packets across the networks. In a classic SDN scenario, a packet along with Flow Table arrives at an Open Flow switch. The Open Flow Table is generally executed with a technology known as Ternary Content Addressable Memory (TCAM). A flow table is typically filled with rules or policies that direct the switch forwarding direction of the packets. These rules or policies to direct the switches are sent to the switch by a centralized controller. A flow table exists in an Open Flow Switch. This flow table has a logical structure of data, and all the packets are transmitted as per a list that shows the prioritized entries. Additionally, the flow table can store flow entries in which each entry is created using 15 field tuples. Some of these fields are elective, but the priority, action, statistical counter, timeout mechanism and matching field are used frequently.